Method for refining long-chain dicarboxylic acid by using mixed solvent

Abstract

The invention discloses a method for refining long-chain dicarboxylic acid by using a mixed solvent, which comprises the following steps: heating and dissolving a long-chain dicarboxylic acid crude product serving as a raw material in an acetonitrile-water mixed solvent, decolorizing and filtering, cooling and crystallizing, separating and washing, and dehydrating and drying to obtain a long-chain dicarboxylic acid refined product. The long-chain dicarboxylic acid product refined by the method disclosed by the invention is high in single acid purity, good in light transmittance, large in stacking density and low in solvent residue, the product quality meets the quality requirements on long-chain dicarboxylic acid in the industrial standard, and the method is suitable for industrial application.

Description

Technical Field

[0001] The invention relates to a refining technology of a long-chain dibasic acid, in particular to a method for refining a long-chain dibasic acid with a mixed solvent. Background Art

[0002] Long-chain dibasic acid is a kind of fine chemical intermediate with important uses. It is an important raw material for synthesizing high-grade fragrances, high-performance nylon engineering plastics, high-grade hot melt adhesives, high-temperature dielectrics, high-grade paints and coatings, high-grade lubricants, cold-resistant plasticizers, resins, medicines and pesticides.

[0003] The crude long-chain dibasic acid obtained by biological fermentation contains impurities such as pigments, proteins and metal ions in the fermentation broth, resulting in poor product quality. Although washing with a large amount of water can improve product quality, it still does not meet the polymer grade quality standards. Secondly, the product is in powder form with a low bulk density. In downstream applications, it is easy to generate dust and has a low loading coefficient, which not only affects the working environment, but also reduces the utilization rate of the equipment.

[0004] During the refining process of long-chain dibasic acids, it is necessary to remove proteins, pigments, inorganic salts and other intermediate metabolites from the crude product. The main refining methods for long-chain dibasic acids are the aqueous phase method and the solvent method. Since long-chain dibasic acids are difficult to dissolve in water, the aqueous phase method is to dissolve the long-chain dibasic acid salts in water for refining and purification. The process conditions are mild, but the product quality is difficult to meet the requirements of polymerization grade. The solvent method uses the crude long-chain dibasic acid as raw material and uses organic solvents to dissolve the long-chain dibasic acid for refining. The long-chain dibasic acid product refined by the solvent method has high purity and can meet the requirements of polymerization grade. The organic solvents currently used mainly include low-carbon alcohols, low-carbon acids, esters, ethers, etc., such as methanol, ethanol, acetic acid, ether, ethyl acetate, butyl acetate and their mixtures and other organic solvents.

[0005] The patent application publication number CN1255483A relates to a method for purifying long-chain dibasic acids from C10-C18 straight-chain alkane fermentation broth by an aqueous phase method. The content of impurities such as protein and pigment in the product is effectively reduced through the long-chain dibasic acid monosalt crystallization step, and a long-chain dibasic acid product with a total acid content of more than 99% and a white appearance is prepared. However, the product has a high color and nitrogen content, which is not suitable for the quality requirements of polymerization-grade products.

[0006] Application publication number CN101985416A discloses a process for refining long-chain dibasic acids produced by a biological fermentation method, wherein acetic acid with a content of more than 90% is used as a solvent, and a crude long-chain dibasic acid product is dissolved in a hot acetic acid solution according to a certain ratio, and a long-chain dibasic acid crystalline product is obtained through activated carbon decolorization, primary crystallization separation, high-temperature water crystallization separation, and drying. The advantage of this method is that the purity of the product reaches more than 98% after refining, and the defect is that there is acetic acid (acetic acid is a monocarboxylic acid) solvent residue in the refined product, and when the downstream produces polymers, the monocarboxylic acid prevents the polymerization reaction from continuing, reduces the molecular weight of the polymer, and affects the performance of the polymer. And the high-concentration acetic acid is extremely corrosive, and the production equipment is titanium and 316L, and the manufacturing price is expensive and the investment is large.

[0007] The patent application publication number CN111349006A discloses a method for refining long-chain dibasic acid, which uses low-carbon alcohol as solvent to purify long-chain dibasic acid. This method has the defect that the long-chain dibasic acid and the low-carbon alcohol undergo esterification reaction at high temperature, which will produce new by-products and affect the purity of the product. Therefore, this method has not been widely used.

[0008] The patent application publication number CN112742062A discloses a method for recrystallizing a long-chain dibasic acid, which uses ethers, low-carbon alcohols and water as a mixed solvent to purify the long-chain dibasic acid. At high temperatures, the long-chain dibasic acid and the alcohol are esterified, and new by-products are also produced during the refining process, affecting the purity of the product. The process route is complex, and negative and positive pressure operations exist during the operation.

[0009] The existing technology for refining long-chain dibasic acids mainly has the following shortcomings:

[0010] 1. When long-chain dibasic acids are refined using water as solvent, the product color and nitrogen content are relatively high, which does not meet the index requirements of downstream customers for polymerization-grade products.

[0011] 2. When long-chain dibasic acids are refined using acetic acid as solvent, the product quality indicators meet the requirements of the downstream customers' polymerization grade indicators, but there is acetic acid residue in the product. When producing polymers downstream, acetic acid prevents the polymerization reaction from continuing, reduces the molecular weight of the polymer, and affects the performance of the polymer. In addition, due to the strong corrosiveness of acetic acid, the equipment investment and distillation energy consumption during solvent recycling are high (the boiling point of acetic acid is 118°C).

[0012] 3. When using low-carbon alcohol as solvent to purify long-chain dibasic acid, alcohol will undergo esterification reaction with long-chain dibasic acid at high temperature, affecting the quality of the product. Summary of the invention

[0013] The object of the present invention is to provide a method for refining long-chain dibasic acid with a mixed solvent to solve the problems raised in the above background technology.

[0014] To achieve the above object, the present invention provides the following technical solutions:

[0015] The invention discloses a method for refining a long-chain dibasic acid by using a mixed solvent. The method comprises heating and dissolving a crude long-chain dibasic acid in a mixed solvent of acetonitrile and water to purify the long-chain dibasic acid.

[0016] As a further embodiment of the present invention, the volume ratio of acetonitrile to the mixed solvent of acetonitrile-water is 50-95%, preferably 55-90%.

[0017] As a further scheme of the present invention: the long-chain dibasic acid refers to one or a mixture of two or more saturated and unsaturated aliphatic organic dicarboxylic acids with a carbon chain length of 10-16, and the crude long-chain dibasic acid refers to a long-chain dibasic acid in the form of powder, granules or filter cake, which is obtained by pretreatment of biological fermentation liquid or chemical synthesis.

[0018] As a further solution of the present invention: the solubility of the crude long-chain dibasic acid in an acetonitrile-water mixed solvent is 5 g / ml to 45 g / ml, and the preferred solubility is 10 g / ml to 40 g / ml.

[0019] As a further solution of the present invention: the dissolution temperature of the crude long-chain dibasic acid is 50-110°C, preferably 70-100°C.

[0020] As a further scheme of the present invention: the decolorization filtration temperature after the crude long-chain dibasic acid is dissolved in an acetonitrile-water mixed solvent is 50-110°C, preferably 70-100°C, the decolorization time is 20-120min, the decolorizer used is activated carbon, activated clay or adsorption resin, and the amount of the decolorizer is 0.1-10w% of the mass of the long-chain dibasic acid raw material.

[0021] As a further embodiment of the present invention, the long-chain dibasic acid is crystallized in an acetonitrile-water mixed solvent, and the temperature range for the start of crystal precipitation is 40 to 95°C, preferably 50 to 80°C.

[0022] As a further solution of the present invention: the control rate of cooling crystallization of the long-chain dibasic acid in an acetonitrile-water mixed solvent is 0.5-20°C / hour, and the crystallization endpoint temperature is 20-30°C.

[0023] As a further solution of the present invention: the crystals crystallized by cooling are separated and washed, and the washing solvent used is pure water, the amount of pure water used is 1 to 6 times the mass of the long-chain dibasic acid raw material, and the temperature of the pure water is 20 to 100°C.

[0024] As a further solution of the present invention: the washed crystals are dehydrated and dried, and the drying temperature is controlled at 50-130°C, preferably 70-120°C.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Based on the characteristic that the solubility of long-chain dibasic acids in a certain proportion of acetonitrile-water mixed solvent varies greatly with temperature, a method for refining long-chain dibasic acids using acetonitrile-water mixed solvent was invented. The process route is simple and easy to apply industrially, opening up a new way to purify long-chain dibasic acids.

[0027] 2. The long-chain dibasic acid refined product obtained by the method of refining long-chain dibasic acid using acetonitrile-water mixed solvent has high monoacid purity, good light transmittance, large product bulk density, good fluidity, and low solvent residue. The quality of the product meets the requirements of industry standard T / CIEP-0034-2023 and meets the polymerization-grade index requirements of downstream customers.

[0028] 3. The boiling point of acetonitrile in the acetonitrile-water mixed solvent is 82.1°C, and the energy consumption of solvent recycling in the acetonitrile-water mixed solvent refining process is low.

[0029] 4. A method for refining long-chain dibasic acid using an acetonitrile-water mixed solvent. The production equipment usually uses 304 material, and the equipment investment is small. However, acetic acid is extremely corrosive, and the production equipment usually uses 316L and titanium, which are expensive to manufacture and require a large equipment investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the solubility of deca-dicarboxylic acid in different acetonitrile-water mixed solvents at 75°C in a method for refining long-chain dibasic acids with mixed solvents.

[0031] Figure 2 This is a schematic diagram of the solubility of deca-dicarboxylic acid in different acetonitrile-water mixed solvents at 25°C in a method for refining long-chain dibasic acids with mixed solvents.

[0032] Figure 3 This is a schematic diagram of the solubility of dodecanedioic acid in different acetonitrile-water mixed solvents at 78°C in a method for refining long-chain dibasic acids with a mixed solvent.

[0033] Figure 4 This is a schematic diagram of the solubility of dodecanedioic acid in different acetonitrile-water mixed solvents at 30°C in a method for refining long-chain dibasic acids with mixed solvents. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] Long-chain dibasic acids are slightly soluble in acetonitrile, and the solubility of long-chain dibasic acids in acetonitrile solvent does not change much with temperature. For example, the solubility of decanedioic acid in 100 ml acetonitrile is 0.14 g at 25°C, and 4 g at 75°C; the solubility of dodecanedioic acid in 100 ml acetonitrile is 0.13 g at 30°C, and only 3 g at 78°C. The present invention has found that the solubility of long-chain dibasic acid in a certain proportion of acetonitrile-water mixed solvent varies greatly with temperature, such as 2.13 g / 100 ml of 10-carbon dibasic acid in 70 v% acetonitrile-30 v% water mixed solvent at 25 ° C, 35 g / 100 ml of 10-carbon dibasic acid in 70 v% acetonitrile-30 v% water mixed solvent at 75 ° C; 0.805 g / 100 ml of 12-carbon dibasic acid in 70 v% acetonitrile-30 v% water mixed solvent at 30 ° C, 31 g / 100 ml of 12-carbon dibasic acid in 70 v% acetonitrile-30 v% water mixed solvent at 78 ° C. The long-chain dibasic acid is refined by using acetonitrile-water mixed solvents of different proportions under certain temperature conditions, and the obtained refined product has high purity, good transmittance, large bulk density, low solvent residue, and is suitable for large-scale production and application.

[0036] In the embodiment of the present invention, w% is the mass percentage, v% is the volume percentage, and a method for refining a long-chain dibasic acid with a mixed solvent is to dissolve a crude long-chain dibasic acid raw material in a mixed solvent of acetonitrile-water, decolorize and filter, cool and crystallize, separate and wash, and dehydrate and dry to obtain a refined product.

[0037] The total acid, monoacid, moisture and total nitrogen detection of the long-chain dibasic acid in the present invention adopts the "China Environmental Protection Promotion Association Group Standard" T / CIEP-0034-2023; acetonitrile solvent residue determination: adopt the Pharmacopoeia 2020 Edition 0521 gas chromatography headspace injection; transmittance determination: take 5 grams of long-chain dibasic acid sample and dissolve it in 20ml dimethyl sulfoxide, and use a spectrophotometer to measure the transmittance at 440nm / 550nm; bulk density determination: adopt GB / T6286-2021 molecular sieve bulk density determination method. Acetic acid solvent residue determination: dissolve the dibasic acid sample in methanol, take the methanol solution, and detect the acetic acid residue content in gas phase. It is necessary to combine acetic acid and methyl acetate for calculation, and refer to the method of GB / T 10345-2007 for specific reference.

[0038] Example 1

[0039] Weigh 2.50 kg of crude decanedioic acid (powder), add 8 liters of mixed solvent with 60% acetonitrile content, add 60 g of activated carbon, heat to 79°C to dissolve the crude decanedioic acid, keep warm and stir to decolorize for 40 minutes, filter to obtain decolorized clear liquid, cool and crystallize, control the crystallization cooling rate to 10°C / hour, and the crystallization end temperature is 23°C. After filtering the crystallized material, wash it with 90°C pure water, and the amount of washing water is 4 times the quality of the crude decanedioic acid. Dry it at 85°C for 6 hours to obtain refined decanedioic acid.

[0040] The crude product (powder) of decacarbonyl dicarboxylic acid has a moisture content of 0.25w%, a total acid content of 99.37w%, a monoacid content of 97.10w%, a total nitrogen content of 322mg / kg, a light transmittance of 59.5% / 71.8%, and a bulk density of 0.31.

[0041] A total of 2.31 kg of refined decacarbonyl dibasic acid was collected, with water content of 0.27 w%, total acid content of 99.58 w%, monoacid content of 99.36 w%, total nitrogen content of 19 mg / kg, acetonitrile residue of 11 mg / kg, transmittance of 99.1% / 99.6%, and bulk density of 0.62.

[0042] Example 2

[0043] Weigh 8.00 kg (dry) of crude decanedioic acid (filter cake), add 30 liters of mixed solvent with 95% acetonitrile content, add 200 g of activated carbon, heat to 79°C to dissolve the crude decanedioic acid, keep warm and stir to decolorize for 60 minutes, filter to obtain decolorized clear liquid, cool and crystallize, control the crystallization cooling rate to 10°C / hour, and the crystallization end temperature is 22°C. After filtering the crystallized material, wash it with 85°C pure water, and the amount of washing water is 3 times the quality of the crude decanedioic acid. Dry it at 105°C for 4 hours to obtain refined decanedioic acid.

[0044] The crude product of decanedicarboxylic acid (filter cake) has a moisture content of 50.90w%, a total acid content of 99.57w%, a monoacid content of 98.30w%, a total nitrogen content of 377mg / kg, and a light transmittance of 57.2% / 69.5%.

[0045] A total of 7.30 kg of refined decacarbonyl dibasic acid was collected, with water content of 0.21 w%, total acid content of 99.78 w%, monoacid content of 99.76 w%, total nitrogen content of 27 mg / kg, acetonitrile residue of 15 mg / kg, transmittance of 99.3% / 99.8%, and bulk density of 0.63.

[0046] Example 3

[0047] Weigh 1200g (dry) of crude decanedioic acid (filter cake), add 4 liters of mixed solvent with 85v% acetonitrile content, add 30g of activated carbon, heat to 80℃ to dissolve the crude decanedioic acid, keep warm and stir to decolorize for 50 minutes, filter to obtain decolorized clear liquid, cool and crystallize, control the cooling rate to 8℃ / hour, and the crystallization end temperature is 20℃. After filtering the crystallized material, wash it with 65℃ pure water, and the amount of washing water is 3 times the quality of the crude decanedioic acid. Dry it at 95℃ for 6 hours to obtain refined decanedioic acid.

[0048] The crude product of decanedicarboxylic acid (filter cake) has a moisture content of 49.70w%, a total acid content of 99.57w%, a monoacid content of 98.42w%, a total nitrogen content of 365mg / kg, and a light transmittance of 57.5% / 68.3%.

[0049] A total of 1092 g of decacarbonyl dibasic acid was collected, with water content of 0.02 w%, total acid content of 99.81 w%, monoacid content of 99.51 w%, total nitrogen content of 19 mg / kg, acetonitrile residue of 12 mg / kg, transmittance of 99.2% / 99.8%, and bulk density of 0.64.

[0050] Example 4

[0051] Weigh 500g of crude decanedioic acid (powder), add 1.7L of mixed solvent with 70v% acetonitrile, add 10g of activated carbon, heat to 79℃ to dissolve the crude decanedioic acid, keep warm and stir to decolorize for 70 minutes, filter to obtain decolorized clear liquid, cool and crystallize, control the cooling rate to 12℃ / hour, until the crystallization end temperature is 25℃. After filtering the crystallized material, wash it with 70℃ pure water, and the amount of washing water is 3 times the quality of the crude decanedioic acid. Dry at 95℃ for 5 hours to obtain refined decanedioic acid.

[0052] The crude product (powder) of decacarbonyl dibasic acid has a moisture content of 0.21w%, a total acid content of 99.71w%, a monoacid content of 98.61w%, a total nitrogen content of 195mg / kg, a light transmittance of 69.2% / 81.1%, and a bulk density of 0.32.

[0053] A total of 457 g of decacarbonyl dibasic acid was collected, with water content of 0.28 w%, total acid content of 99.85 w%, monoacid content of 99.47 w%, total nitrogen content of 27 mg / kg, acetonitrile residue of 15 mg / kg, transmittance of 99.2% / 99.7%, and bulk density of 0.65.

[0054] Example 5

[0055] Weigh 5.00 kg of crude decanedioic acid (granules), add 20 liters of mixed solvent with 65% acetonitrile content, add 100 g of activated carbon, heat to 75°C to dissolve the crude decanedioic acid, stir and decolorize for 60 minutes, filter to obtain decolorized clear liquid, cool and crystallize, control the cooling rate to 8°C / hour, until the crystallization end temperature is 22°C. After filtering the crystallized material, wash it with 65°C pure water, and the amount of washing water is 4 times the quality of the crude decanedioic acid. Dry at 105°C for 4 hours to obtain refined decanedioic acid.

[0056] The crude product (granules) of decacarbonyl dicarboxylic acid has a moisture content of 0.29w%, a total acid content of 99.71w%, a monoacid content of 98.72w%, a total nitrogen content of 35mg / kg, a light transmittance of 92.1% / 98.2%, and a bulk density of 0.63.

[0057] A total of 4.59 kg of deca-dicarboxylic acid was collected, with 0.10 w% moisture, 99.82 w% total acid, 99.71 w% monoacid, 9 mg / kg total nitrogen, 10 mg / kg acetonitrile residue, 99.3% / 99.9% transmittance and 0.65 bulk density.

[0058] Example 6

[0059] Weigh 5.00 kg of crude 11-dicarboxylic acid (powder), add 50 liters of mixed solvent with 50% acetonitrile, add 150 g of activated carbon, heat to 95°C to dissolve the crude 11-dicarboxylic acid, keep warm and stir to decolorize for 50 minutes, filter to obtain decolorized clear liquid, cool and crystallize, control the cooling rate to 10°C / hour, until the crystallization end temperature is 24°C. After filtering the crystallized material, wash it with 80°C pure water, and the amount of washing water is 5 times the quality of the crude 11-dicarboxylic acid. Dry it at 85°C for 6 hours to obtain refined 11-dicarboxylic acid.

[0060] The crude product (powder) of undecanedicarboxylic acid has a moisture content of 0.11w%, a total acid content of 99.52w%, a monoacid content of 97.52w%, a total nitrogen content of 297mg / kg, a light transmittance of 72.9% / 81.5%, and a bulk density of 0.30.

[0061] A total of 4.53 kg of undecanedicarboxylic acid was collected, with 0.13 w% moisture, 99.89 w% total acid, 99.30 w% monoacid, 23 mg / kg total nitrogen, 16 mg / kg acetonitrile residue, 99.2% / 99.7% transmittance and 0.62 bulk density.

[0062] Example 7

[0063] Weigh 2.00 kg (dry) of crude 11-dicarboxylic acid (filter cake), add 8 liters of mixed solvent with 85% acetonitrile content, add 55 g of activated carbon, heat to 70°C to dissolve the crude 11-dicarboxylic acid, decolorize with stirring for 60 minutes, filter to obtain decolorized clear liquid, cool and crystallize, control the cooling rate to 6°C / hour, and the crystallization end temperature to 20°C. After filtering the crystallized material, wash it with 80°C pure water, and the amount of washing water is 4 times the quality of the crude 11-dicarboxylic acid. Dry it at 85°C for 6 hours to obtain refined 11-dicarboxylic acid.

[0064] The crude product of undecanedicarboxylic acid (filter cake) has a moisture content of 48.60w%, a total acid content of 99.27w%, a monoacid content of 97.21w%, a total nitrogen content of 409mg / kg, and a light transmittance of 58.5% / 69.7%.

[0065] A total of 1.82 kg of undecanedicarboxylic acid was collected, with 0.22 w% moisture, 99.65 w% total acid, 99.41 w% monoacid, 22 mg / kg total nitrogen, 15 mg / kg acetonitrile residue, 99.1% / 99.6% transmittance and 0.63 bulk density.

[0066] Example 8

[0067] Weigh 10.00 kg of crude dodecanedioic acid (powder), add 40 liters of mixed solvent with 85% acetonitrile content, add 220 g of activated carbon, heat to 78°C to dissolve the crude dodecanedioic acid, keep warm and stir to decolorize for 70 minutes, filter to obtain decolorized clear liquid, cool and crystallize, control the cooling rate to 12°C / hour, to the crystallization end temperature of 28°C. After filtering the crystallized material, wash it with 80°C pure water, the amount of washing water used is 4 times the quality of the crude dodecanedioic acid. Dry at 105°C for 4 hours to obtain refined dodecanedioic acid.

[0068] The crude product (powder) of dodecanedioic acid has a moisture content of 0.25w%, a total acid content of 99.3w%, a monoacid content of 97.40w%, a total nitrogen content of 275mg / kg, a light transmittance of 76.3% / 85.6%, and a bulk density of 0.33.

[0069] A total of 9.27 kg of dodecanedioic acid was collected, with 0.17 w% moisture, 99.41 w% total acid, 99.63 w% monoacid, 21 mg / kg total nitrogen, 17 mg / kg acetonitrile residue, 99.3% / 99.8% transmittance and 0.65 bulk density.

[0070] Example 9

[0071] Weigh 1200g of crude dodecanedioic acid (powder), add 4.5 liters of mixed solvent with acetonitrile content of 75v%, add 30g of activated carbon, heat to 79°C to dissolve the crude dodecanedioic acid, keep warm and stir to decolorize for 50 minutes, filter to obtain decolorized clear liquid, cool and crystallize, control the cooling rate to 8°C / hour, to the crystallization end temperature of 29°C. After filtering the crystallized material, wash it with 60°C pure water, and the amount of washing water is 4 times the quality of the crude dodecanedioic acid. Dry it at 95°C for 5 hours to obtain refined dodecanedioic acid.

[0072] The crude product (powder) of dodecanedioic acid has a moisture content of 0.15w%, a total acid content of 99.37w%, a monoacid content of 97.22w%, a total nitrogen content of 187mg / kg, a light transmittance of 69.1% / 78.9%, and a bulk density of 0.32.

[0073] A total of 1115 g of dodecanedioic acid was collected, with water content of 0.22 w%, total acid content of 99.47 w%, monoacid content of 99.52 w%, total nitrogen content of 19 mg / kg, acetonitrile residue content of 21 mg / kg, transmittance of 99.2% / 99.8%, and bulk density of 0.64.

[0074] Example 10

[0075] Weigh 4.00 kg (dry) of crude dodecanedioic acid (filter cake), add 15 liters of mixed solvent with 90% acetonitrile content, add 100 g of activated carbon, heat to 79°C to dissolve the crude dodecanedioic acid, keep warm and stir to decolorize for 60 minutes, filter to obtain decolorized clear liquid, cool and crystallize, control the crystallization cooling rate to 12°C / hour, and the crystallization end temperature is 30°C. After filtering the crystallized material, wash it with 75°C pure water, and the amount of washing water is 5 times the quality of the crude dodecanedioic acid. Dry it at 105°C for 4 hours to obtain refined dodecanedioic acid.

[0076] The crude product of dodecanedioic acid (filter cake) has a moisture content of 48.70w%, a total acid content of 99.33w%, a monoacid content of 98.10w%, a total nitrogen content of 325mg / kg, and a light transmittance of 65.1% / 76.7%.

[0077] A total of 3.68 kg of refined dodecanedioic acid was collected, with water content of 0.21 w%, total acid of 99.55 w%, monoacid of 99.56 w%, total nitrogen of 22 mg / kg, acetonitrile residue of 18 mg / kg, transmittance of 99.2% / 99.7%, and bulk density of 0.65.

[0078] Embodiment 11

[0079] Weigh 700g of crude tridecanedioic acid (powder), add 2.4 liters of mixed solvent with acetonitrile content of 75v%, add 15g of activated carbon, heat to 78°C to dissolve the crude tridecanedioic acid, keep warm and stir for 60 minutes for decolorization, filter to obtain decolorized clear liquid, cool and crystallize, control the cooling rate to 10°C / hour, to the crystallization end temperature of 25°C. After filtering the crystallized material, wash it with 75°C pure water, and the amount of washing water is 5 times the quality of the crude tridecanedioic acid. Dry it at 100°C for 5 hours to obtain refined tridecanedioic acid.

[0080] The crude product (powder) of tridecanedioic acid has a moisture content of 0.25w%, a total acid content of 99.30w%, a monoacid content of 97.65w%, a total nitrogen content of 291mg / kg, a light transmittance of 73.2% / 83.1%, and a bulk density of 0.31.

[0081] A total of 645 g of tridecanedioic acid was collected, with water content of 0.25 w%, total acid content of 99.28 w%, monoacid content of 99.46 w%, total nitrogen content of 25 mg / kg, acetonitrile residue of 9 mg / kg, transmittance of 99.2% / 99.7%, and bulk density of 0.63.

[0082] Example 12

[0083] Weigh 2.00 kg (dry) of crude tridecanedioic acid (filter cake), add 7 liters of mixed solvent with 85% acetonitrile content, add 50 g of activated carbon, heat to 78°C to dissolve the crude tridecanedioic acid, keep warm and stir for 60 minutes to decolorize, filter to obtain decolorized clear liquid, cool and crystallize, control the crystallization cooling rate to 7°C / hour, and the crystallization end temperature is 29°C. After filtering the crystallized material, wash it with 78°C pure water, and the amount of washing water is 4 times the quality of the crude tridecanedioic acid. Dry it at 90°C for 6 hours to obtain refined tridecanedioic acid.

[0084] The crude product of tridecanedioic acid (filter cake) has a moisture content of 49.20w%, a total acid content of 99.25w%, a monoacid content of 97.46w%, a total nitrogen content of 318mg / kg, and a light transmittance of 66.2% / 77.5%.

[0085] A total of 1.81 kg of refined tridecanedioic acid was collected, with water content of 0.27 w%, total acid content of 99.65 w%, monoacid content of 99.66 w%, total nitrogen content of 22 mg / kg, acetonitrile residue of 17 mg / kg, transmittance of 99.3% / 99.8%, and bulk density of 0.64.

[0086] Example 13

[0087] Weigh 5.00 kg (dry) of crude tetradecanedioic acid (powder), add 30 liters of mixed solvent with 80% acetonitrile content, add 120 g of activated carbon, heat to 80°C to dissolve the crude tetradecanedioic acid, stir and decolorize for 50 minutes, filter to obtain decolorized clear liquid, cool and crystallize, control the cooling rate to 6°C / hour, until the crystallization end temperature is 20°C. After filtering the crystallized material, wash it with 70°C pure water, and the amount of washing water is 4 times the quality of the crude tetradecanedioic acid. Dry it at 105°C for 4 hours to obtain refined tetradecanedioic acid.

[0088] The crude product (powder) of tetradecanedioic acid has a moisture content of 8.00w%, a total acid content of 99.30w%, a monoacid content of 97.26w%, a total nitrogen content of 210mg / kg, a light transmittance of 76.5% / 85.4%, and a bulk density of 0.33.

[0089] A total of 4.60 kg of tetradecanedioic acid was collected, with water content of 0.25 w%, total acid of 99.65 w%, monoacid of 99.45 w%, total nitrogen of 16 mg / kg, acetonitrile residue of 17 mg / kg, transmittance of 99.3% / 99.8%, and bulk density of 0.62.

[0090] Embodiment 14

[0091] Weigh 500g (dry) of crude 15-carbon dicarboxylic acid (powder), add 2.5 liters of mixed solvent with acetonitrile content of 70v%, add 15g of activated carbon, heat to 79°C to dissolve the crude 15-carbon dicarboxylic acid, keep warm and stir for 60 minutes for decolorization, filter to obtain decolorized clear liquid, cool and crystallize, control the cooling rate to 7°C / hour, until the crystallization end temperature is 22°C. After filtering the crystallized material, wash it with 75°C pure water, and the amount of washing water is 5 times the quality of the crude 15-carbon dicarboxylic acid. Dry it at 95°C for 5 hours to obtain refined 15-carbon dicarboxylic acid.

[0092] The crude product (powder) of pentadecanedioic acid has a moisture content of 7.50w%, a total acid content of 99.62w%, a monoacid content of 96.75w%, a total nitrogen content of 230mg / kg, a light transmittance of 73.2% / 84.1%, and a bulk density of 0.31.

[0093] A total of 457 g of pentadecanedioic acid was collected, with water content of 0.13 w%, total acid content of 99.77 w%, monoacid content of 99.15 w%, total nitrogen content of 19 mg / kg, acetonitrile residue of 11 mg / kg, light transmittance of 99.2% / 99.7%, and bulk density of 0.63.

[0094] Embodiment 15

[0095] Weigh 1.50 kg (dry) of crude 15-carbon dicarboxylic acid (filter cake), add 6 liters of mixed solvent with 85% acetonitrile content, add 40 g of activated carbon, heat to 85°C to dissolve the crude 15-carbon dicarboxylic acid, decolorize with stirring for 60 minutes, filter to obtain decolorized clear liquid, cool and crystallize, control the cooling rate to 6°C / hour, to the crystallization end temperature of 28°C. After filtering the crystallized material, wash it with 77°C pure water, and the amount of washing water used is 4 times the quality of the crude 15-carbon dicarboxylic acid. Dry at 90°C for 6 hours to obtain refined 15-carbon dicarboxylic acid.

[0096] The crude product of pentadecanedioic acid (filter cake) has a moisture content of 49.72w%, a total acid content of 99.22w%, a monoacid content of 96.12w%, a total nitrogen content of 370mg / kg, and a light transmittance of 67.2% / 79.1%.

[0097] A total of 1.35 kg of pentadecanedioic acid was collected, with water content of 0.24 w%, total acid content of 99.17 w%, monoacid content of 99.11 w%, total nitrogen content of 27 mg / kg, acetonitrile residue of 26 mg / kg, light transmittance of 99.1% / 99.5%, and bulk density of 0.63.

[0098] Example 16

[0099] Weigh 200g of crude 16-carbon dicarboxylic acid (powder), add 3.5L of mixed solvent with 75v% acetonitrile, add 10g of activated carbon, heat to 82℃ to dissolve the crude 16-carbon dicarboxylic acid, decolorize with stirring for 60 minutes, filter to obtain decolorized clear liquid, cool and crystallize, control the cooling rate to 5℃ / hour, until the crystallization end temperature is 25℃. After filtering the crystallized material, wash it with 80℃ pure water, and the amount of washing water is 4 times the quality of the crude 16-carbon dicarboxylic acid. Dry at 100℃ for 5 hours to obtain refined 16-carbon dicarboxylic acid.

[0100] The crude product (powder) of hexadecanedioic acid has a moisture content of 0.27w%, a total acid content of 99.37w%, a monoacid content of 97.52w%, a total nitrogen content of 182mg / kg, 72.4% / 83.5%, and a bulk density of 0.32.

[0101] A total of 179 g of hexadecanedioic acid was collected, with water content of 0.12 w%, total acid content of 99.58 w%, monoacid content of 99.42 w%, total nitrogen content of 17 mg / kg, acetonitrile residue of 25 mg / kg, transmittance of 99.1% / 99.6%, and bulk density of 0.65.

[0102] Comparative Example 1

[0103] Refined decacarbonyl dibasic acid was obtained according to the method of Example 4, except that 99w% acetic acid was used as the solvent instead of the mixed solvent with 70v% acetonitrile, and the heating and dissolving temperature was 87°C.

[0104] A total of 451 g of decacarbonyl dibasic acid was collected, with a moisture content of 0.15 w%, a total acid content of 99.75 w%, a monoacid content of 99.37 w%, a total nitrogen content of 25 mg / kg, an acetic acid residue of 367 mg / kg, a light transmittance of 99.1% / 99.6%, and a bulk density of 0.55.

[0105] Comparative Example 2

[0106] Purified dodecanedioic acid was obtained according to the method of Example 9, except that 99w% acetic acid was used as the solvent instead of the mixed solvent with 75v% acetonitrile, and the heating and dissolving temperature was 88°C.

[0107] A total of 1087 kg of dodecanedioic acid was collected, with 0.19 w% moisture, 99.86 w% total acid, 99.49 w% monoacid, 33 mg / kg total nitrogen, 359 mg / kg acetic acid residue, 99.1% / 99.6% transmittance and 0.55 bulk density.

[0108] Comparative Example 3

[0109] Purified tridecanedioic acid was obtained according to the method of Example 11, except that 99w% acetic acid was used as the solvent instead of the mixed solvent with 75v% acetonitrile content, and the heating dissolution temperature was 86°C.

[0110] A total of 633 g of tridecanedioic acid was collected, with water content of 0.22 w%, total acid content of 99.72 w%, monoacid content of 99.44 w%, total nitrogen content of 37 mg / kg, residual acetic acid content of 286 mg / kg, transmittance of 99.1% / 99.7%, and bulk density of 0.54.

[0111]

[0112] As can be seen from the above table, the long-chain dibasic acid product refined by the method of the present invention has high monoacid purity, good product transmittance, low solvent residue, and the product quality meets the "China Industrial Environmental Protection Promotion Association Group Standard"

[0113] T / CIEP-0034-2023, meeting the index requirements of downstream customers’ aggregation level.

[0114]

[0115] It can be seen from the above table that the long-chain dibasic acid product purified by the method of the present invention has a high yield, a large bulk density and low solvent residue.

[0116] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for refining long-chain dibasic acid using a mixed solvent, characterized in that: The crude long-chain dibasic acid is heated and dissolved in a mixed solvent of acetonitrile-water to purify the long-chain dibasic acid.

2. The method for refining long-chain dibasic acid using a mixed solvent according to claim 1, characterized in that: The volume ratio of acetonitrile to the mixed solvent of acetonitrile-water is 50-95%, preferably 55-90%.

3. The method for refining long-chain dibasic acid using a mixed solvent according to claim 1, characterized in that: Long-chain dibasic acid refers to one or a mixture of two or more saturated and unsaturated aliphatic organic dicarboxylic acids with a carbon chain length of 10-16. Crude long-chain dibasic acid refers to a long-chain dibasic acid in the form of powder, granules or filter cake, which is obtained by pretreatment of biological fermentation liquid or chemical synthesis.

4. The method for refining long-chain dibasic acid using a mixed solvent according to claim 1, characterized in that: The solubility of the crude long-chain dibasic acid in an acetonitrile-water mixed solvent is 5 g / ml to 45 g / ml, and the preferred solubility is 10 g / ml to 40 g / ml.

5. The method for refining long-chain dibasic acid with a mixed solvent according to claim 1, characterized in that: The dissolution temperature of the crude long-chain dibasic acid is 50-110°C, preferably 70-100°C.

6. The method for refining long-chain dibasic acid with a mixed solvent according to claim 1, characterized in that: The decolorization filtration temperature after the crude long-chain dibasic acid is dissolved in an acetonitrile-water mixed solvent is 50-110°C, preferably 70-100°C, and the decolorization time is 20-120min. The decolorizing agent used is activated carbon, activated clay or adsorption resin, and the amount of the decolorizing agent is 0.1-10w% of the mass of the long-chain dibasic acid raw material.

7. The method for refining long-chain dibasic acid with a mixed solvent according to claim 1, characterized in that: The long-chain dibasic acid is crystallized in an acetonitrile-water mixed solvent, and the temperature range for the start of crystal precipitation is 40 to 95°C, preferably 50 to 80°C.

8. The method for refining long-chain dibasic acid with a mixed solvent according to claim 1, characterized in that: The controlled rate of cooling crystallization of the long-chain dibasic acid in an acetonitrile-water mixed solvent is 0.5-20°C / hour, and the crystallization endpoint temperature is 20-30°C.

9. The method for refining long-chain dibasic acid using a mixed solvent according to claim 1, characterized in that: The crystals crystallized by cooling are separated and washed, and the washing solvent used is pure water, the amount of pure water used is 1 to 6 times the mass of the long-chain dibasic acid raw material, and the temperature of the pure water is 20 to 100°C.

10. The method for refining long-chain dibasic acid with a mixed solvent according to claim 1, characterized in that: The washed crystals are dehydrated and dried, and the drying temperature is controlled at 50-130°C, preferably 70-120°C.

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